FIG. 3 is a diagram showing a part of a cross section of a conventional loudspeaker. In this loudspeaker, voice coil body 22 movably disposed on magnetic circuit 21 is coupled to the inner peripheral end of diaphragm 23. The outer peripheral end of diaphragm 23 is coupled to frame 25 via edge 24. The back surface of diaphragm 23 is coupled to frame 25 via suspension holder 26 and edge 27. The projecting shapes of edges 24 and 27 are pointed to opposite directions, and hence the upside and downside of the amplitude of diaphragm 23 are vertically symmetric. Thus, the acoustic strain of the loudspeaker is reduced. Such a loudspeaker is disclosed in Japanese Patent Unexamined Publication No. 2004-7332, for example.
In such a loudspeaker structure, suspension holder 26 is formed of a rigid body with a rigidity equivalent to that of diaphragm 23. Therefore, the additional mass of diaphragm 23 is increased, and hence the driving load is increased on magnetic circuit 21. As a result, it is difficult to improve the driving efficiency of the loudspeaker.